The invention relates to an omnibus with an air conditioning system having an intake port placed at the rear row of seats of the omnibus and opening into the space in the omnibus provided for the passengers.
At the rear and over the engine space such a fully air conditioned omnibus has a space for the accommodation of the air conditioning unit which includes a powerful blower to cause circulation of the air within the omnibus.
This interior air is taken in through at least one suction port which is placed at the rear row of seats in the partition separating the said space for the air conditioning unit from the passenger space, that is to say in the rear end wall of the omnibus.
The cleaned and cooled air is propelled by the said blower through a duct arranged along the roof to the air outlet nozzles provided for the individual passenger seats.
In order to ensure that front seats at the greatest distance from the blower are amply supplied with conditioning air, it is necessary for the circulating blower to build up a substantial pressure. Since on the other hand, more especially in hot countries there is a substantial heating of the passenger space owing to solar radiation and the high temperature of the outside air which makes its way into the interior of the omnibus, it is furthermore necessary for the circulation blower to have a very high volumetric capacity. Since the blower is designed for a high circulation rate to meet this requirement, it will necessarily be loud in operation, and the noise engendered by it will also be heard through the intake port or ports. Furthermore the air velocity at the intake port will often by relatively high so that a considerable amount of noise will arise as the air flows through the nozzle. These two sources of noise lead to a substantial interference with the comfort of the passengers using the rear row of seats in the interior of the bus.
A further point to be considered is that the powerful air flow being drawn into the intakes will be a cause of discomfort for such passengers and, to take one instance, cigarette smoke exhaled by such persons will be blown back into their faces. Moreover, the effect of the air outlet nozzles, which are intended to supply conditioned air to the persons using the rear seat row is considerably interfered with by the air drawn in from the interior to be air conditioned; futhermore the persons on the rear row of seats will be constantly exposed to the heated stale air in the interior of the omnibus. On the other hand in the foot space of the rear seat row a zone of practically stationary air builds up, in which cold air sinks downwards so that the persons on the rear seat row have to put up with cold feet in addition to the noise from operation of the air conditioning system and the presence of unconditioned air at the level of the chest and head.
Some of these undesired effects might be made less severe if the air intake port were to be increased in size, but then it would be necessary to have a bulky air duct running from the intake port to the circulating blower, which would not be able to be accommodated in the space for the air conditioning unit.